京 都 大 学 防 災 研 究 所 年 報 第 50 号 B 平 成 19 年 4 月
Annuals of Disas. Prev. Res. Inst., Kyoto Univ., No. 50 B, 2007

The Process of Community’s Coping Capacity Development in the SumidaWard, Tokyo – A Case Study of Rainfall Harvesting Movement
Subhajyoti SAMADDAR* and Norio OKADA*

Graduate School of Engineering, Kyoto University

Synopsis
The rainwater harvesting movement in the Sumida Ward, Tokyo helps local community to
reduce water related risks, and also to fill up required water supply for the community. In thispaper, we will try to show how this movement diffuses in the community and how this
diffusion process reflected in social network system helps the community to cope with disaster
related risks. This is assumed to be a process where a community shifts from one structuralsituation to another. A survey design is proposed for future empirical study, which isconsidered as juxtaposition of Vitae System Model and social networks approach to understandthe coping capacity of the people.
Keywords: coping capacity, disaster risk management, Vitae System, social networks
1.

Introduction

Coping is defined as the characteristics ofindividuals or groups in terms of their capacity toanticipate, cope with, resist and recover from theimpacts of hazards (Blaikie et al., 1994). Using andenhancing this capacity is a better alternative while
fighting with various disaster risks. In the context ofintegrated disaster risk management, it isaccordingly inevitable to understand this process of
coping mechanism. We consider coping mechanism
is a process of structural change developed by social
networks among the members of that particular
structural unit. An innovative idea or technology,
devolved by a local community to fight with various
disaster risks, is such a reflection of this coping
mechanism in our present study. Our study aims tounderstand the process of diffusion of innovationreflected in the personal networks of adopters as wellas in the whole system networks and also to find out
the factors that influence this process. We have taken
the rainwater harvesting practice by the local
community of Sumida city, Tokyo as our case study.
2.

Problem Description

2.1 Disaster risks in the Sumida Ward, Tokyo
Sumida Ward (Sumida-ku) is located in the easternpart of Tokyo. It has a population of 225,935 persons(as of December, 2001).Being a part of the Tokyo(Metropolitan) City, the Sumida Ward is confronted byvarious disaster and environmental risks in the courseof urbanization. The major disaster risks that have been
faced by the Sumida city are as follows:
Situation – 1 (Water Scarcity): Water supply in theTokyo City largely depends on constructing dams in
the upstream region of the Tone and Tame Rivers.
Until quite recently the numbers of dams haveincreased to meet up the continuously-growing waterrequirements of Tokyo population. But the shade ofresorting to this commonly used countermeasure byutilizing a huge amount of money, manpower andmoney, instead of securing adequate water for the city
was that it forced displacement of people anddevastation of vast areas of farmland in the upstream
region. Moreover, the dams have gradually beenloosing water storage capacity due to continuous silt
deposition. Thus, the process will ultimately bringregional imbalance and environmental insecurity
among the communities of the city, even if, the city ofTokyo and its surrounding regions still need adequate－ 205 －

water to sustain.
Situation – 2 (Flood): The city has more than twobillion cub.ic meters of rainfall every year. Rainwater
is directed to the sewage system and released intorivers. Consequently, the flow exceeds the river system,
resulting in floods. Floods challenge this modern
mega-city and may paralyze the efficient transportsystem, safe drinking water, performing daily activities
etc.
Situation –3 (Water and environmental
contamination): Since the vast lands of the city area
have been covered by asphalt, it is a reason ofhindrance for groundwater recharging. In 70’s when
Japan was enjoying unprecedented economic growth,
factories and buildings pumped up groundwater fromdeep wells excessively disregarding nature’s water
circulation. Consequently, shallow wells dried up
resulting in subsidence, for example- part of Sumida
Ward sank by 3.5m at the deepest.
2.2 Rainwater harvesting– an initiative
Perceiving the risks, Murase, a sanitary officer inthe ‘Sumida City Office’ and a local leader also, cameup with an answer i.e., the practice of rainwater
harvesting. With the help of other colleagues in thecommunity, he organized a group called ‘Raindrop’ tospread the rainwater harvesting practice. Their notionis that instead of discharging the rainwater into thesewage, rain can be caught where it drops and thus
storing rainwater at household level and in community
level small dams can contribute like a big dam in total.
The ‘mini dam’ (tank) is easy to set up and not hugemoney is required. The stored water can be used forwashing, cleaning purpose as well as drinking water inthe emergency and also for fire fighting. On the one
hand, it reduces water caring costs, provides aself-sufficient community, and on the other hand it
helps the community members to mingle with eachother and thus they can share their ideas and feelings.
As a whole, it contributes to the enhancement ofawareness among the community members about theimportance of effective water management. The
rainwater harvesting in the Sumida Ward is not
restricted only at the household level, but it has beenpracticed also at community level. The form ofcommunity level water recycling practice is named‘Rojison’. ‘Roji’ means street and ‘Son’ corresponds to“Respect” in Japanese language, thus it means theobject of roadside respect. . Rojison as a physicalobject has served as a symbol of encouraging
community level water harvesting practice. It is also
a symbol of neighborhood safety and protection
Rainwater is collected in an underground tank, with
rainfall water transferred from roofs of nearby houses.
The water thus stored on-site can be pumped up with ahand pump. Above all, ‘Rojison’ serves a as public
place where the community members can share theirideas, problems and interests.
2.3 Adoption of rainwater harvesting
The idea of rainwater recycling first came into
practice in 1982 when the “Raindrop’ group requested
the sumo (wrestlers’) association to use the rooftop
water of local sumo stadium for non drinking purpose.
Though initially the idea was rejected by the sumo
association, yet the ‘Group Raindrop’ was success to
implement their plan by sanctioning it as a rule throughthe Tokyo Metropolitan Authority. Since then all the
newly constructed public and private buildings havecome under the rainwater recycling system. To date,
180 tanks have been installed and the entire facilities
through the city now hold a volume of 10000 cubic
meters of water. More than 19 Rojison have been built
and used by the communities in Sumida Ward, Tokyo.
Now, Sumida Ward can store 3500 tons of rainwatercaught on the roofs of large building like the
Kokugikan (Sumo hall) and the Edo-Tokyo Museum in
Ryojoku. About 70% of the Kokugikan (SumoWrestling Arena) today use only rainwater. Other large
buildings like Sumida city hall have also beenequipped with basement rainwater tanks. To promote
this practice among the community, various workshops
have been organized; plumbers, engineers, architects
have been trained to construct rainwater recyclingtanks. Social links have been established with various
national and international organizations that are also
practicing rainwater recycling.
3.

Vitae System Model and Coping
Mechanism

3.1 Vitae System Model
Vitae System Model developed by Okada andextended by Misra and Okada (2005) argues that theprocess of reducing disaster vulnerability should be
dovetailed into the very process of community－ 206 －SCHEMA OF VITAE SYSTEM

Communication (To Live Together)

SystemCollapse

Vitality (To Live)

Survival( To Be Alive)
A

i

ll

h lf filib iiFig. 1 Vitae system model (source: Okada and Misra),development. The scope of the perspective is centeredaround holistic viewpoint that any community has
three vital or generic components viz, ‘Survival’,‘Vitality’ and ‘Communication’. ‘Survival’ implies ‘tobecome alive ’, ‘Vitality’ implies ‘to live lively’ and‘communication’ corresponds ‘to live together’. For acommunity to become disaster resilient, thedevelopment of the community must address thecoordinated quality of these three components viz,
‘Quality of Survival’ (QUS), ‘Quality of Vitality’(QUV), and ‘Quality of Communication’ (QUC).
Excessive inadequacy of any of the components could
result in the collapse of the system. Though securing
the ‘Quality of Survival’ is considered one of the prime
objectives, yet a balance growth of all threecomponents is essential for a resilient system moving
along towards a desirable development (Fig. 1).
3.2 Sumida crisis-turned chance development in
the light of ‘Vitae’ system
The Sumida water related crisis shows quite
factually that inappropriate managing of water
resources was leading towards increased vulnerability
to and degraded coping capacity with andenvironmental risks by damaging three components ofthe community as described in the ‘Vitae’ systemmodel. The threats towards the ‘Quality of Survival’(QUS) include such hazards as water scarcity, flood,
fire etc. Similarly, such environmental hazards likedegradation of water quality due to inadequate sewers
and lack of awareness of proper waste disposal andrecycling, all are classifiable as threats to QUS.
Moreover this old community in Sumida Ward has
been confronted by social threats such as potential
displacement of people to outside if some large-scaleurban redevelopment project is straightforwardly
introduced. Notably all of this could have worked as
survival risks to the community but some people werecreative and imaginative enough to turn it otherwise.
The Rojison mini-facility actually was an innovation
which came out of this kind of drive.
On the other hand, meeting the challenge to
upgrade the ‘Quality of Vitality’ (QUV) by both
economically and socially vitalizing this community
has long been an important concern for both local
people and the Sumida Ward Government. At
community level what people can lead and change forthis purpose is limited but effective if graduallyconducted on a modest scale. For instance, efforts toimprove the quality of neighborhood life in terms ofamenity, aesthetics, and amusement are typicalmeasures for achieving the purpose. In fact the“Rojison” community monument has exactly served
for this kind of purpose. People gathered around it,
small children joyfully played with water tapped fromthe facility, and thus it has been regarded as a“neighborhood forum.”All of this forced both local people, local
government officials and concerned specialists to findout an adequate balance between what can be governedat their neighborhood community level and what not,which means that the latter agenda should becommunicate with people living outside and morearea-wide administrative bodies. Knowing this, it wasquite natural and reasonable for them to take on thechallenge towards the ‘Quality of Communication’(QUC). A noteworthy success in this line of challenge
was that the spirits and thoughts of what has been
symbolized by the “Rojison” facility has spread andbecome well accepted in other neighboring Wards.
Though it was not actualized in the form of “Rojison”
facility, the movement also exerted an immense impact
on the rest of the neighborhood community yet within
the same ward or on its neighboring areas, such thatnew buildings and offices have started to implement
water recycling practices (as mandated by the newly
introduced ward-level regulation.).
Two more points need to be made in this regard.
i) It probably helped trigger pro and con publicdebates about emerging limits to the conventional
approach to develop water resources in the Tokyo
Metropolitan Region, and resultant needs for
shifting toward some more distributive and－ 207 －

? How is it

networked utilization system.
ii) Nation-wide and cross-country-wide social
networks of people (citizens, government officials,
NGOs, specialists, etc.) have been constantly
extending to advocate, promote and sharerainwater harvesting knowledge and technology.
This is an encouraging example of upgraded QUC
which promoted dissemination and collaboration far
beyond the community area.
3.3 Rainwater harvesting as an integrated
approachNow, it better to review the above points derived
from application of the Vitae System Model and toturn up our focus to the most essential point of what
the Vitae System Model prescribes. That is, any
thing that is modeled as a living body must be
coordinated and integrated in terms of the above
three cardinal functions. This is particularly the casewith modeling the process of its coping capacity
being challenged and likely to become either
upgraded or degraded.
How does the rainwater practice in the Sumida
Ward help the community to fill up the quality ofstructural components by using their own local
resources and capacities? The rainwater harvesting
movements guided the community into maintaining
and enhancing its structural requirements through abalance development or progress of its various
components. This functional integration process may
be explained as follows: reducing flood risk,
recharging ground water, in-situ water storage which
resulted in the improvement and maintenance of the‘Quality of Survival’.
Similarly “Rojison” served as an instrument forthe social and economic vitalization of thecommunity. Being a “neighborhood forum”, it
provided the community a physical sphere to gather
around, share their ideas and values, use watertapped from the facility for watering plants,
cleanings cars and public places. It rendered theopenings to improve the quality of neighborhood life
in terms of amenity, aesthetics which are elements ofthe ‘Quality of Vitality”.
In a due course, the spirits and thoughts that has
been symbolized by the “Rojison” facility has spreadin other neighboring wards. Implementation of water
harvesting practices in the new buildings and offices

Rainwater
tank

Scenario – 1
No idea?

Good

Scenario – 2

?

Good

Good

No idea

Bad
Scenario – 3

Adopted –It’s good

Scenario – 4
Fig. 2 Getting information from others helps anindividual to take decision by about aninnovative idea

exemplifies the sprits communicated within the sameward or its neighboring areas. The social networks
have been established between communities,
government officials, NGOs, specialists etc. atnation and international level to advocate, encourage
and uphold the idea of rainwater harvestingknowledge and technology. This is a stirring
example of upgraded ‘Quality of Communication’.
3.4 Rainwater harvesting – ‘a stock of knowledge’or technology
We now turn our discussion to highlight on the
aspect of “innovation” made through the above
mentioned community movement symbolized by
rainwater harvesting.
A technology is a design for instrumental actionthat reduces the uncertainty in the cause-effectrelationship involved in achieving a desired outcome(Rogers, 1983). It is argued by the scholars (Rogers,1983) that a technology has two components viz.,hardware and software. Hardware consists of toolsthat embody technology as a material and physicalobject; and software includes the knowledge base for－ 208 －

the tool. Thus, we consider the rainwater harvestingis a ‘stock of knowledge’ or a technology. It is
knowledge in a sense that by performing the above
mentioned function, it may help the local community
to maintain their structural components such as QUS,QUV and QUC. The rainwater recycling is thus ameans for the community for its structural change.
This structural change is on the other hand an
outcome of the coping mechanism of the local
community in a scenario where the rainwater
recycling is a tool or a stock of knowledge.
Rainwater harvesting may help the community toshift from one structural position to another, or it
helps the community to maintain their structuralcomponents as well as to reduce future risks.
4.

Diffusion of rainwater harvesting and social
networks

Community’s coping mechanism is a result of theprocess of adoption of rainwater tank (mini dam) as
well as the practice of community water harvesting like‘Rojison’ in the Sumida Ward. As evidenced in theprevious discussions based on the Vitae System Model,
the community is considered to become more resilientas people increasingly adopt this innovative idea. To
understanding of this knowledge and technology as aninnovation process is necessary to conceptualize thecoping mechanism of the community. The diffusion ofknowledge and technology is defined as the process bywhich a few members of a social system initially adopt
an innovation, then over the time more individuals
adopt until all members adopt the new idea (Ryan and
Gross, 1943; Rogers, 1983; Valente, 1995). Here, we,consider the diffusion of knowledge and technology or
the adoption of rainwater harvesting by the community
members as the change in coping capacity.
An innovation is defined as an idea, practices, orobjects that are perceived as new by an individual orother unit of adoption (Rogers, 1983). This newness
aspect contains a degree of uncertainty. The“Newness” aspect of an innovation may be expressedin terms of knowledge, persuasion, or decision to adopt.
So, in a diffusion process, the degree of uncertainty canbe reduced by obtaining information or observing the
adoption behavior of others. In Fig – 2, we have shown
how we interpret an individual takes decision about the
adoption of an innovation. For example, in the firstscenario (Fig.2), seeing the rainwater tank, an
individual person becomes curious about that, but he or
she is unable to take decision because he or she does
not have any information on that aspect. The figure
shows that in the following process, he/she starts togather information from his/her peer group orneighbors. Relying on others information andobserving others’ behavior, he/she comes to his/herdecision and adopts the new idea. Sharing informationby the members of a social system in such a way that it
creates a chain of network that helps the members of
the system to take a collective decision about the newidea. Modeling this network pattern within thisnetwork frame is instrumental to understand the patternof the diffusion process or the process of changing
coping capacity.
A social network is the pattern of friendship, advice,communication or support which exists among themembers of a social system (Knoke and Kuklinski,
1982; Burt and Minor, 1983; Wellman 1988; Valente,1996). How do social networks influence diffusion?
Becker (1970) mentioned the association between
socio-metric location or social network and diffusionof innovation in at least three ways. First, interpersonalcommunications provide the network individual withinformation that he/she might otherwise have missed.
Second, the knowledge that others have considered
and/or introduced, and the concept being transmitted
provide this individual with legitimating and support.
Finally, location in the network of interpersonal
relations exposes the individual to deliberate influenceattempts concerning acceptance or disapproval of theinnovation.
5.

Threshold model of diffusion of innovation

5.1 Threshold model of diffusion of innovation
In the beginning of social network approach ofdiffusion in innovation study, a significant numberof researchers tried to focus on opinion leader i.e., tocount the number of times an individual was
nominated as a network partner and to correlate
this variable with innovativeness as measured by anindividual’s time of adoption of the innovation understudy ( Valente, 1996). Opinion leader was theorized
to be a significant influence on the rate of adoption.
In a diffusion process, all the individuals do notnecessarily adopt the innovation at the same time;－ 209 －

rather it is adopted by a person or group ofindividuals in the beginning and later on, othermembers of the community follow them. An
individual engages in a behavior based on the
proportion of people in the social system alreadyengaged in the behavior (Granovetter, 1982). Thus,
an individual, while adopting the new idea, observes
the behavior of the members of his/her own
community, which helps him/her to reduce
uncertainty accompanied with the newness aspect ofa technology or innovation. Therefore, anindividual’s adoption behavior is a function of the
behaviors of others in a group. This approach ofdiffusion of innovation was postulated by
Granovetter (1978). Focusing on the structural
approach, Granovetter introduced the thresholdmodel of collective behavior. A collective threshold
behavior is the proportion of adopters in a system
prior to an individual’s adoption. Individuals whoare very innovative, have adopted the innovative
idea or technology when none or very few of its
network members adopt. It recognizes an individualwith a low threshold, whereas, a high thresholdperson adopts the innovation when a majority of his
network members adopted the innovation.
Granovetters (1983) postulates the threshold is the
proportion of adopters in the social system needed
for an individual to adopt an innovation. Valente(1996) argued that the problem of this collective
behavior threshold is that the individual may not beable to accurately observe the behavior of others in asocial system and thus he/she relies much on his/her
personal network for taking a decision on adoptionof the innovation. Since the innovation contains
uncertainty, it encourages individuals to discuss withothers who have already adopted and have someexperience (Becker, 1970). As a result, the adoption
threshold must be measured in terms of directcommunication links with others in contrast tocollective behavior threshold (Valente, 1996).
Personal network is the set of direct ties that anindividual has within a social system (Wellman, 1988).
In the course of diffusion of innovation, more andmore people adopt the innovation and as a result the
proportion of adopters in an individulas’s personal
network generally increases. But this process depends
on the structure of the system. Fig. 3 shows thisprocess of adoption in an individual’s personal network.

Exposure is the proportion of adopters in an
individual’s personal network at a given time. Since
adoption threshold is the proportion of adopters in an
individual’s personal network, an individual is thus
very innovative if none of his/her personal network
members adopted the innovation at the time of his/heradoption, i.e., he/she is a very radical person as well asa low threshold individual. On the contrary, anindividual is considered as very conservative if all themembers of his/her personal network adopted theinnovation before he/she adopted (Fig.4). But, aperson’s degree of innovativeness depends not only at
the personal level, but also at the system level. A
person may be very innovative in respect of his/her
personal networks, but not so innovative in respect of
the whole system and vis-a–vis. Therefore, thedegree of innovativeness should be judged both inrespect of personal network as well as system network.
5.2 Adopter categorization
Classical diffusion of innovation study classified
adopters based on innovativeness as measured by－ 210 －a) time 1 ,exposure = 0%b) time 2 ,exposure = 40%c) time 3 ,exposure = 80%d) time 4 ,exposure = 100%
threshold = 100%

Fig. 3 Showing exposure and threshold in personal
network (source: Valente, 1996)

Conservative(very high threshold)

Average ,(Median threshold)

Very innovative,(very low threshold)Fig. 4 Degree of innovative inpersonal network

time-of-adoption (Rogers, 1983).
Adopters areclassified as 1) early adopters, 2) early majority, 3) latemajority, and 4) laggards. Early adopters areindividuals whose time-of-adoption is greater than one
standard deviation earlier than the averagetime-of-adoption. Early and Late majorities areindividuals whose time-of-adoption is bounded by one
standard deviation earlier and later than the average.
Laggards are those individuals who adopted later than
one standard deviation from the mean. Valentine(1996) classified personal network threshold adoptersby partitioning the network thresholds distribution in
the same manner describe for time-of-adoption adopter
categories. Low network threshold individuals havepersonal network thresholds one standard deviation
lower than the average threshold. Low and highnetwork threshold individuals have personal network
thresholds bounded by one standard deviation less thanand greater than average. High network thresholdindividuals have personal network thresholds one
standard deviation greater than average (The average
threshold is the mean threshold for the community).
Adopter categorization is created to compare early
adopters with later adopters to determine difference intheirsocialandpersonal
characteristics,
communication behavior and opinion leadership.
5.3 External influence
Two possible external sources of influence on
adoption of innovations are cosmopolitan actions andcommunication media. A cosmopolitan individual isoriented to the world outside of his/her local social
system and relates his/her local social system to thelarger environment by providing links to outside
information (Valente, 1996). Cosmopolitan actions andmedia consumption provide individuals with earlier
awareness of an innovation (Becker, 1970). External
influence may have different impacts on the diffusionof innovations in the personal networks and systemlevel. Role of external influence on adoption of
innovation needs to be clarified when one considers
thresholds relative to the social system and personal
networks (Valente, 1996). This dual classification
permits specification of how external and interpersonal
influence flow through the system and govern the
diffusion of innovations.

6.

A proposed survey design

6.1 Required data
Empirical analysis of the personal network
threshold model requires data collected on – 1) timeof Adoption, 2) individual attributes 3) social
network ties , 3) external influence.
6.2 Survey design
It is quite comprehensible that using the thresholdmodel of the Sumida rainwater harvesting diffusion
process will provide us with a give us a picture tounderstand the coping capacity of the community.
Here, we propose a preliminary idea of conducting theempirical survey in the Sumida Ward. For our study,
we plan to take a neighborhood of the Sumida Ward.
For the statistical analysis to be meaningful, the sample
size needs to be large enough. One idea is to cover thewhole or a lesser population the survey area, which
may be identical to this neighborhood or much smaller.
In this regard, it is required to mention that the survey
area community should be practically a closed groupso that the ties among the community members arepresent.
6.3 Time of adoption
The information about time of innovation will becollected by asking people to recall their time of
adoption rainwater of a recycling tank, and if possible,
the month and year of adoption specified. This
information will help us to categorize the adopters bothat personal level and system level.
6.4 Individual attributes
Individual’s personal attributes are very muchconcerned with time of adoption. The degree ofinnovativeness depends on personal characters of the
adopters (Coleman et al, 1957). Considering this, weare planning to collect the data by individuals
attributes such as age, sex, occupation, income,education level, the frequency of attending
workshops organized by the ‘Raindrop Group’, etc. .
To find out the individual motive of rainwater
adoption, we also intend to categorize the individuals
by relying on the structural components of the‘Vitae’ system. We propose to categorize theindividuals motives into three orientation viz
survival orientation, vitality orientation and－ 211 －

communication orientation. To capture thisphenomenon, the individual will be asked to answer
the following question (one example):
How would you rank the importance of thesecharacteristics in using the rainwater recycling? a) It helps to deal with any water related disaster risk
(QUS)b) It reduces the water utility expenditure (QUV)c) I have adopted it or will adopt it as because myfriend/neighbor requested or advised (QUC)
The following response patterns in ranking will beclassified as follows: - Survival oriented – abc, acb;
Vitality oriented – bca, bac; and Communication
oriented- cba, cab.
The classification of the individual according totheir orientation will give us a better picture about
the process of diffusion. Arguing over this point, wehere presented one hypothetical scenario (Fig. 5) thatshows the co-relation between individual’sorientation and time of adoption of a rainwater tank.
We assume that a group of individuals adopt the
rainwater recycling at different periods of time andeach of them has one’s own orientation for the
adoption. Fig. 5 shows a hypothetical distribution of
the adopters both at the personal level (personal
networks) and system level (collective networks) incorrelation with the adopter’s orientation. A
hypothetical figure of the diffusion process of arainwater tank shows that in the case of personal
network the majority of the very early adopters arecommunication oriented, yet at system level the
majority of the early adopters are survival oriented.
So in this way, the intention of the adopters in theinitial phase can be determined by correlating theirtime of adoption and orientation. It may help
illustrate that what factors or orientations play crucialrole in the diffusion process. For example, thehypothetical figure shows that at the system level,
initially the adopters were vitality oriented, but as theprocess progressed, the adopters became much morecommunication oriented. We may work with such a
scenario that can predict that at the system level inthe initial stage the survival factors plays a morecrucial role than others , but in a later stage ofdiffusion process, maintaining quality ofcommunication or the communicative motive of theindividuals with the others serves as the major factor
of diffusion of innovation. In this way, thePersonal Level

System Level

C

C

Early
Adopters
S

C

V

S

C

V

Early
MajorityS

Late
Majority
S

C

C

S

S

C

C

V

V

Laggards

S= Survival oriented= Vitality oriented= Communication
oriented

SV= Vitae System-Modeled Adopter
S = Survival
V = Vitality
C=Communication

Fig. 5 A Hypothetical relation between individuals’
orientation and time of adoption
categorization of individual attributes in threeorientations will enable us to judge or understand thevarious aspects of diffusion processes. For the sakeof our discussion, we have only shown anddiscussed single hypothetical scenario developed
from the correlation between classification of theorientation of the individuals and the time of
adoption.
6.5 Social network ties
The importance of social network ties has alreadybeen mentioned above in this paper. Direct ties i.e.
personal networks among the individuals as well as theindirect ties among the individuals likewise system
networks are the reflection of individuals’ behavioral
pattern. However, ties between individuals in a social
network are not commonly homogonous. The patternof network among the members in a system varies－ 212 －

Table 1 Proposed survey design for social network ties
Concepts
Quality ofsurvival

Variables
Water requirements( physical infrastructure )Quality ofvitality

Efficient water utility

Quality ofcommunication

Friendship (social
interaction)

Survey design
Whom (3 persons) does he (the respondent) often turn foradvice and suggestion in water/ infrastructure related
problem?
Whom (3 persons) does he (the respondent) think mosteffectively used the water recycling or handled water
problem?
Who (3 persons) are the friends in this neighborhood,whom he (the respondent) saw or interact most oftensocially?

according to the changes of the nature of ties. An
individual likes to develop tie with others in various
contexts. The changes in the nature of ties also
influence the pattern of social networks in acommunity. Therefore, we categorize the informalties among the members in a system into three aspects
based on the three structural components of the ‘Vitae’
system. Table-1 shows the three different network ties
and proposed a survey design accordingly.
The significance of categorization of social networkties is not only restricted to understanding thecorrelation between the nature of ties and network
patterns. It also gives an idea how the opinion leaders
are changing with the changing nature of ties. It. may
be the individuals who are nominated as opinion
leaders in the case of ‘survival’ tie, but in the case ofother two cases such as vitality and communication ties,
other individuals may possibly be identified as opinion
leaders. It also helps us to find out the relation between
opinion leaders in various social ties and theirindividual attributes or orientation. Thus it raises aquestion that is there any relation between diffusion of
innovation and the present condition of community
structure? Our tentative answer is: yes, quite likely,
and the clue is to make use of the ‘vitae’ structure.
With this in mind, our proposed survey is expected toaddress the following questions:a) How does an individual seek social ties to maintaintheir structural components?
b) How his /her adoption decision depends on his/her
location in a social structure, the designed survey cananswer these questions?
7.

movements impacted the community and otherexternal areas. It has been shown that this entire
process can be interpreted as an innovation processwith the symbolic technology of rainwater
harvesting being diffused and disseminated.
A
point is made that the Vitae System Model is useful
in describing and modeling the integration process of
three cardinal functions which are considered tocharacterize the coping capacity of a community orsocial system of our focus.
We have also referred to the importance ofunderstanding the ongoing structural change and thatof addressing a community’s coping capacity
development. The proposed social network approachhelps us systematically study the behavioral natureof a community through analysis of social network
patterns .It is also mentioned that in our study,
instead of considering an actor as monogamous node,
we considered it as a dynamic unite of a social
structure. Putting individual’s attributes, motives,
behavioral action and ability into the light of the‘Vitae System’ structure, our study has suggested aprospective analytical method to model a more
dynamic nature of the social network To understanda community’s coping mechanism, it is necessary tounderstand these dynamic components of an actor,
instead of simply considered as a static node of aholistic structural pattern. Our future work will
include an empirical survey actually conducted in
Sumida city based on the above mentioned proposed
study design, and then examine if we can derive
meaningful policy implications.
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東京都墨田区におけるコミュニティの取り組み能力開発のプロセスに関する研究– 雨水活用運動をケーススタディとしてスブハジョティ サマッダル*・岡田 憲夫*

京都大学大学院工学研究科

要 旨
東京都墨田区における雨水活用運動によって、雨水を集め、内水排除対策、渇水対策等に寄与することを目的としている。本研究は、このようなミニ技術の普及伝播のプロセスに着目し、これを技術革新過程とみなすとともに、社会的ネットワークの変容が災害リスクへの取り組み能力にも影響し、ひいては社会的ネットワークの構造が変化するという見方でモデル分析する。実証的研究を行うために社会調査を設計する必要に触れるとともに、生命体システムの諸機能の具体的な特定や社会的ネットワークと地域の災害リスクへの取り組み能力の変化との具体的な意味づけについても議論する。

キーワード: 取り組み能力, 災害のリスク管理, 生命体システム, 社会的ネットワーク－ 215 －